1. Field of the Invention
The present invention relates to an image-forming apparatus and a light beam scanning apparatus.
2. Description of the Related Art
For example, a laser scanning apparatus (equivalent to a light beam scanning apparatus) provided in a laser printer as an image-forming apparatus has such a configuration as shown in FIG. 8. That is, laser light L (represented by the solid-line arrow in FIG. 8) emitted from a laser light source 1 passes through a cylindrical lens 2 so as to be incident on a deflection surface 3a of a polygon mirror 3. The laser light L reflected on the deflection surface 3a is converged by imaging optical systems 4 and 5 so that an imaging spot Ps is formed on a photosensitive drum surface 6 as an image carrier. The imaging spot Ps is scanned on the photosensitive drum surface 6 as the polygon mirror 3 rotates.
The laser light L incident on the photosensitive drum surface 6 is scattered and reflected on the photosensitive drum surface 6. The scatter-reflected light La (represented by the broken-line arrow in FIG. 8) is transmitted through the imaging optical systems 4 and 5 and returns to the polygon mirror 3 side. On this occasion, part of the scatter-reflected light La is reflected on a deflection surface (hereinafter referred to as “adjacent deflection surface 3b”) adjacent to the deflection surface 3a so that the angle of reflection of the part of the scatter-reflected light La is different from that of the laser light L. The reflected light Le is transmitted through the imaging optical systems 4 and 5 so as to be incident on a point Pg on the photosensitive drum surface 6. Incidentally, the reflected light Le is always concentrated on the point Pg regardless of the angle of incidence of the laser beam L on the deflection surface 3a of the polygon mirror 3.
Accordingly, the reflected light Le act so that a ghost image different from an original electrostatic latent image is formed on the photosensitive drum surface 6. This may cause deterioration of image-forming quality.